Hyperparameter tuning. Same Bookings Forecast and Tuned Bookings but Best MAPE better

Hello

I have following examples after we run Hyperparameter tuning:

The Tuned Bookings Forecast has not been changed but the Tuned Best MAPE is lower (better) than the Tuned Base MAPE.

We are reporting a MAPE improvement with this example even if Forecast was not adjusted in any way.

Is the engine assuming that there will be a future improvement based on the parameter setting even though not yet translated in Bookings Forecast?

Thank you